A forensic glass analysis is typically a comparison of two or more glass fragments in an attempt to determine if they originated from different sources. Less frequently, it is a question of determination of end use, or glass provenance.
How is glass used in forensic science?
If a window or glass object is broken or shattered by a projectile, such as a bullet, the breakage pattern can be analyzed to possibly determine the angle of trajectory of the projectile, shedding more light on the crime, such as where the suspect was when the gun was fired.
Why is glass analysis used in forensic science?
Glass fragments at a crime scene should always be collected and analyzed because several clues can be gathered about the events that occurred during the crime. Fragments of glass from headlights at a hit-and-run scene can leave clues about the unknown vehicle.
What are the two most often used methods of glass analysis?
The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, respectively.
What are the method used for matching of glass evidence?
(g/cm3 (solids); g/mL (liquids)) • One method of matching glass fragments is by a density comparison. Each type of glass has a density that is specific to that glass. If two samples of glass can be differentiated by density, they could not have originated from the same source.
What is the 3r rule?
The three R’s stands for: Reduce, Reuse and Recycle. This rule is part of the waste hierarchy which is a process used to protect the environment and conserve resources through a priority approach. The aim is to get the most practical benefits from products and to generate the minimum amount of waste.
What are the 2 types of glass fractures cracks?
When a projectile i.e. a bullet or rock hits the glass, it will form two distinct types of fractures: Radial and Concentric. There is another terminology that is known as cone fracture, observed to be caused by a penetration of the high velocity projectile such as a bullet.
What are the 4 types of glass?
There are four main types or strengths of glass:
- Annealed Glass. Annealed glass is a basic product formed from the annealing stage of the float process. …
- Heat Strengthened Glass. Heat Strengthened Glass is semi tempered or semi toughened glass. …
- Tempered or Toughened Glass. …
- Laminated Glass.
What is a normal line forensics?
normal line. a line drawn perpendicular to the interface surface of two different media.
What is the 4R rule?
Answer: The 4R means Reduce, Reuse, Recycle and Restore. (i) Reduce: We should reduce the use of non-biodegradable compounds that are harmful to us.
What are stress marks in glass?
Stress marks, seen on a cross section of a glass fracture, are shaped like arches that are perpendicular to one glass surface and curved nearly parallel to the opposite surface. The importance of stress marks stems from the observation that the perpendicular edge always faces the surface on which the crack originated.
What type of glass is heat resistant?
Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), making them more resistant to thermal shock than any other common glass.
What property is used to identify glass and match it to glass at a crime scene?
Refractive index is the most commonly measured property in the forensic examination of glass fragments (Koons et al. 2002), because: Precise refractive indices can be measured rapidly on the small fragments typically found in casework.
Where is glass evidence stored?
Place small glass fragments in paper bindles, then in coin envelopes, pill boxes, or film cans which can be marked and completely sealed. Place large glass fragments in boxes. Separate individual pieces with cotton or tissue to prevent breakage and damaged edges during shipment.
What is the importance of glass evidence?
Purpose The value of glass fragments as evidence is not always fully recognized. Windows, automobile glass, broken bottles, and other glass objects may be crucial evidence in burglary, murder, hit-and-run and many other types of crime.
Why is glass class evidence?
Very small glass fragments would not fit together well, some fragments would probably not be found at all. This would make it more difficult to put the pieces together and match to the rest of the bottle; so this is class evidence.